This application claims the priority of Japanese Patent Application No. 6-225926 filed on Aug. 25, 1994 which is incorporated herein by reference.
1. Field of the Invention
The present invention relates generally to a nonaqueous electrolyte battery comprising a negative electrode having lithium as an active material and, more particularly, to an improved nonaqueous electrolyte for improving low-temperature discharge characteristics of the battery.
2. Description of the Prior Art
A nonaqueous electrolyte conventionally used for a nonaqueous electrolyte battery comprising a negative electrode having lithium as an active material contains, for example, such kind of solute as lithium tetrafluoroborate (LiBF.sub.4) or lithium perchlorate (LiClO.sub.4) dissolved in a mixed solvent consisting essentially of a relatively high-boiling solvent such as propylene carbonate, .gamma.-butyrolactone or sulfolane and a relatively low-boiling solvent such as 1,2-dimethoxyethane or tetrahydrofuran.
A major drawback of conventional nonaqueous electrolytes of that kind is that they are apt to react with negative electrode materials resulting in undesirable surface layer formation on the negative electrode which increases the electric resistance of the interface between the negative electrode and nonaqueous electrolyte. For this reason, conventional nonaqueous electrolyte batteries have posed such a problem that it is difficult to withdraw a large amount of current at low temperatures and their low-temperature discharge capacities are low.
Having intensively studied this problem, we, the inventors, have discovered that the reaction between a nonaqueous electrolyte and negative electrode materials can be suppressed by use of a mixed solvent having a specific composition in the nonaqueous electrolyte.